With cranes, their longitudinal structural parts such as the tower or the boom are as a rule composed of a multiple of pieces to achieve a better transportation capability. The longitudinal structural pieces, which can in particular be configured as latticework carriers or frame carriers, in this respect often comprise horizontal beams or corner arms which are placed next to one another at the front face or end face on assembly and which are connected to one another by a mortise and tenon joint. In this respect, a projecting tongue is provided at the horizontal beam or corner arm of the one piece and moves into a tongue receiver which is provided at the other horizontal beam or corner arm to be connected thereto and which can, for example, be formed by the inner space of the horizontal beam or corner arm frequently formed as a hollow section or by a connection piece involved therein. In this respect, tower parts or boom parts of a crane frequently each have a plurality of such horizontal beams or corner arms which may extend in parallel with one another and which are connected to one another by transverse connectors, for example in the form of bars. Tower parts of tower slewing cranes, for example, frequently have a rectangular cross-section which is defined by four corner arms which are connected to one another by transverse and diagonal bars. The four corner arms of such a tower piece are connected in the named manner to the four corner arms of a next tower piece by four mortise and tenon joints.
It is understood that the named mortise and tenon joints should be configured as precisely and as free of tolerances as possible in order not to impair the stability of the longitudinal structural part and thus the support capability of the crane however, limits often being set by production tolerances since excessive press fits are not acceptable and would impair the assembly or dismantling.
It is therefore the underlying object of the present invention to provide an improved crane of the said kind which avoids disadvantages of the prior art and further develops the latter in an advantageous manner. The mortise and tenon joint for connecting the tower pieces or boom pieces should in particular be improved such that a higher support capability is achieved without sacrificing the assembly-friendliness.
This object is achieved in accordance with the invention by a crane in accordance with claim 1. Preferred embodiments of the invention are the subject of the dependent claims.
It is therefore proposed to configure the crossbar securing the mortise and tenon joint as spreadable to be able to clamp or tension to one another the mortise and tenon joints and then the pieces of the longitudinal structural part to be connected. While a preloaded connection of the structural part pieces can be achieved by spreading apart the cross bolt or crossbar, the non-spread apart state of the crossbar allows a simple assembly and dismantling, including joining and releasing the mortise and tenon joints. In accordance with the invention, the crossbar of the mortise and tenon joint can be spread apart by a spreading device such that the pieces of the longitudinal structural part to be connected can be clamped to one another by spreading apart the crossbar. The spreading apart of the crossbar is accompanied by a widening or an increase in the cross-section of the crossbar which, on the one hand, secures the crossbar itself to the tongue or to the tongue receiver and, on the other hand, clamps the tongue and the tongue receiver to one another and thus the structural part pieces to one another. The structural part pieces can be held by a compressive force on one another. The support capability of the crane can be considerably improved by such a clamping of the structural part pieces to be connected.
The crossbar can in particular—when viewed in the inserted state—be able to be spread apart in the longitudinal direction of the tongue and/or in the longitudinal direction of the longitudinal structural part such that the tongue can be drawn or pressed into the tongue receiver and the pieces of the longitudinal structural part to be connected to one another can be clamped to one another in its longitudinal direction. The spreading of the crossbar transversely to its longitudinal direction is therefore oriented such that the corner arms or horizontal beams to be connected are clamped end face to end face or the longitudinal structural parts to be connected are clamped with respect to one another at the end faces. The longitudinal structural part pieces are held on one another by a compressive force due to the tensioning, with said compressive force considerably increasing the support capability of the longitudinal structural part and thus of the crane.
The spreading device or the crossbar which can be spread apart can generally be configured differently to achieve the desired spreading apart capability. In accordance with an advantageous further development of the invention, the crossbar can comprise at least two spreading parts which are displaceable relative to one another in the longitudinal direction of the crossbar and which comprise at least one oblique surface which converts a relative movement of the spreading parts with respect to one another in the named longitudinal direction of the crossbar into a spreading movement transverse to the named longitudinal direction of the bar. The named oblique surface can in this respect in particular be inclined at an acute angle with respect to the longitudinal axis of the crossbar to be able to spread apart the outer contour of the crossbar in accordance with the wedge principle.
The named oblique surface can in this respect have different contours, for example in the form of a conical oblique surface in the manner of a drill chuck or, for example, such that a spreading cone can be inserted into an inner recess of a crossbar sleeve which can, for example, be longitudinally slit and which can be spread apart by inserting the spreading cone.
In an advantageous further development of the invention, the oblique surface can, however, also form a slanted longitudinal sectional plane through the crossbar and/or can be formed such that the spreading apart of the crossbar substantially takes place one-dimensionally, i.e. the cross-sectional dimension of the crossbar increases in a plane on a spreading part of the crossbar and remains substantially the same in a plane perpendicular thereto. By spreading apart the crossbar, its extent in the longitudinal direction of the tongue and/or in the longitudinal direction of the longitudinal structural part can in particular be increased while the crossbar dimension in the direction transverse to the named longitudinal axis remains substantially the same. The oblique surface or wedge surface can in particular be approximately planar.
In an advantageous further development of the invention, the two named spreading parts of the crossbar can form spreading wedges which can be displaced with respect to one another in the longitudinal direction of the crossbar and which can slide off one another, optionally with the interposition of an intermediate piece. The two spreading wedges can in particular form crossbar half-shells seated on one another which are arranged in opposite directions to one another or which are seated on one another in opposite directions, i.e. whose thinner ends face the oppositely disposed sides of the crossbar. The two crossbar half-shells can together form an approximately pin-like crossbar which is divided into the two named half-shells by a longitudinal sectional plane or oblique surface which is slanted or which extends at an acute angle with respect to the longitudinal pin direction.
The crossbar can, however, also comprise more than two such spreading parts in a further development of the invention, in particular three, but optionally also more than three, spreading parts which are displaceable relative to one another in the longitudinal direction of the crossbar and which advantageously each comprise oblique surfaces which are each aligned transversely with respect to a common spreading plane so that the spreading effect of the plurality of oblique surfaces moves in the same direction or acts in a common spreading plane so that the widening of the crossbar is in turn substantially one-dimensional in the aforesaid manner.
On a configuration of the crossbar with three or more spreading parts, in particular a middle wedge having two oppositely disposed wedge surfaces or oblique surfaces can be arranged between two outer wedges which can both be oriented in opposite directions with respect to the named middle wedge, i.e. whose thinner ends face to one side while the thin end of the middle wedge faces the oppositely disposed side. The two outer wedges can in particular bound a V-shaped intermediate space between them in which the named middle wedge is seated.
The spreading parts of the crossbar can generally have different cross-sections, for example an angled, in particular a rectangular, cross-section. To achieve a better distribution of the surface pressures occurring due to the spreading effect, the spreading parts of the crossbar can, however, also have an approximately crescent-shaped cross-section or a semi-oval cross-section or can at least have a rounded side surface or wall side or shell side, in particular having an approximately semicircular contour, at least about the spreading-apart axis in an advantageous further development of the invention.
The named spreading parts can in particular be planar on the rounded sides and oppositely disposed sides or can have oblique surfaces which are of an approximately planar design.
The named preferably crescent-shaped contouring can be provided for both spreading parts with a two-part configuration of the crossbar. If the crossbar is composed of three or more spreading parts, in particular the two outermost spreading parts can have the named approximately crescent-shaped cross-sectional contouring.
Viewed overall, the crossbar can have a cross-sectional contouring differing from the circular shape. However, on the one hand, an incorrect insertion of the crossbar into the reception provided therefore in the tongue or the tongue reception of the mortise and tenon joint can be avoided. On the other hand, it can be ensured on the spreading apart of the crossbar in one direction that the crossbar is still seated with an exact fit in the tongue or in the tongue receiver or in the crossbar receiver provided therein in a direction perpendicular thereto.
The crossbar can in particular have an approximately oval cross-section viewed overall which results from the sum of the cross-sections of the spreading parts seated on one another, in particular the two approximately crescent-shaped spreading wedges and the middle wedge optionally provided therebetween.
The orientation of the cross-section of the crossbar differing from the circular shape is advantageously selected in this respect such that the crossbar has a main cross-sectional axis which extends approximately in parallel with the longitudinal direction of the tongue and/or with the longitudinal direction of the structural part. If the crossbar is provided with an approximately oval cross-section in the named manner, the long main axis of the oval can extend in parallel with the longitudinal axis of the tongue or of the structural part.
In this respect, reception cut-outs for the named at least one crossbar can be provided in the tongue and/or in the tongue receiver or in the wall surrounding the tongue receiver so that the crossbar can be plugged into the crossbar through the tongue receiver, preferably completely through the tongue and through the walls of the tongue receiver surrounding at oppositely disposed sides.
The named plug-in or plug-through cut-out for the crossbar is in this respect advantageously matched in shape to the cross-section or to the cross-section contour of the crossbar. The named plug-through cut-out in the tongue and/or in the tongue receiver can in particular be formed in elongate hole shape in cross-section, with the longer main axis of this plug-through cut-out having a contour in the manner of an elongate hole advantageously being able to extend approximately in parallel with the longitudinal axis of the tongue or of the longitudinal axis of the longitudinal structural part.
To achieve the previously explained longitudinal tensioning of the longitudinal structural part pieces to be connected to one another, a slightly offset arrangement of the plug-through cut-outs in the tongue and in the tongue receiver of the mortise and tenon joint can be provided in an advantageous further development of the invention, in particular such that the plug-through cut-outs in the tongue and in the tongue cut-out are spaced apart by different distances from the end surfaces with which the pieces of the longitudinal structural part are to be spanned on one another so that a flush overlap can only be achieved under a preload by spreading apart the crossbar. The plug-in cut-out for the crossbar in the tongue or its marginal contour provided toward the tongue base can in particular be arranged closer to the end face of the horizontal beam or corner arm having the tongue than the plug-in opening for the crossbar in the tongue receiver of the other corner arm or horizontal beam cooperating therewith is spaced apart from the end-face connection contour provided there. If the two tower pieces or boom pieces are placed loosely at one another and are inserted with the tongues at the corner arms or horizontal beams into the corresponding tongue cut-outs, the margins of the plug-in cut-out are still not exactly flush. This flush alignment or flush placing over one another is only approximately achieved by spreading apart the inserted crossbar or the offset is reduced a little when the crossbar is spread apart, which is accompanied by the desired pre-load of the structural part pieces to be connected.
The adjustment movement for spreading apart the crossbar can generally be generated in different manners. For this purpose, the spreading device can comprise adjustment means for delivering at least a part of the crossbar in the longitudinal direction of the crossbar, with the named adjustment means advantageously being able to comprise an adjustable tie rod, preferably in the form of a screw, with which one of the spreading parts of the crossbar can be displaced relative to another spreading part. For this purpose, an abutment part can in particular be provided which abuts one of the spreading parts at the end face, on the one hand, and which supports the named tie rod or the named screw, on the other hand, so that the other spreading part can be moved toward the abutment by delivering the tie rod or the screw. Only the spreading parts of the crossbar are hereby advantageously acted on relative to one another by the adjustment or drive forces, whereas a corresponding introduction of the forces into the structural parts is not necessary. The abutment intercepts the adjustment force and its reaction force.
The named abutment can be formed, for example, in the form of a hoop part which can surround the corner arm or the horizontal beam of the longitudinal structural part in the region of the connection point. The named abutment can be secured at at least one of the longitudinal structural part pieces, for example by a screw connection, to avoid an unintentional slipping out of the crossbar.
The invention will be explained in more detail in the following with respect to preferred embodiments and to associated drawings.